1. Field of the Invention
A sensor for intravascular residence is disclosed along with methods for percutaneous deployment of the sensor. In preferred embodiments, the sensor is a fiber-optic glucose sensor which is inserted and resides in a peripheral vein without an indwelling cannula.
2. Description of the Related Art
Despite advances in glucose detection technologies, there are no minimally invasive, accurate, real-time, in vivo sensors on the market for monitoring glucose levels over a period of days or weeks. Consequently, it has been a significant burden on diabetics, patients and hospital staff to perform frequent blood sampling for conventional ex vivo blood glucose monitoring. There are short-term continuous glucose sensors that use enzyme-based glucose detection in the interstitial fluid. However, such sensors are relatively large, complex and expensive. These electrochemical sensors also consume reactants (e.g., glucose), which may become limiting particularly when the sensors are walled off due to the patient's foreign body reaction. Moreover, the equilibration lag time may change and the correlation between blood and interstitial glucose levels may become tenuous, particularly in seriously ill (e.g., ICU) patients.
Intravascular sensor deployment raises other technical difficulties. Typically, one sensor for each analyte has been placed in a patient's blood vessel(s) through an indwelling cannula. If it is desired to measure several analytes, a plurality of sensors are often required, which can cause attendant discomfort to the patient and complexity of the electronic monitoring equipment. Moreover, even the deployment of a single sensor within a peripheral vein presents continuous maintenance issues for the nursing staff. The present state of the art is that sensors are deployed through indwelling cannulas. Because blood becomes trapped and clots within such cannulas and between the cannula and the sensor, the cannula must be flushed continuously or periodically, typically with saline/heparin. In the ICU, for example, the nursing staff regularly purge (e.g., every 4 hrs) the trapped blood and clots, to maintain cannula access to the vein open.
Accordingly, there remains an important unmet need for a sensor configured for intravascular deployment and methods of deploying such a sensor, wherein the sensor by itself is left to reside within the vein, without any additional structural components (e.g., an indwelling cannula).